摘要
本文把发生在广西岩溶区的小震级(Ms≤3.0)高烈度(Ⅰ≥Ⅳ)的地震称之为特殊地震。列举了大量特殊地震的震害。根据岩溶区介质的特性,对地震波的传播作了分析;对岩溶区和非岩溶区台站记录到同等震级的地方震的波形做了最大熵谱分析。结果认为:广西岩溶区之所以产生特殊地震,其一、岩溶区饱含水的介质层对地震波具有放大作用。其二、岩溶区的地震波的卓越周期大于外岩溶区的卓越周期,这一卓越周期更接近地面3层以下的楼房的固有周期。由于这些原因,造成烈度偏高。
Geologically Guangxi is a karstic region, where small earthquakes with magnitude M≤3. 0 but high intensity (IV - VI) occurred and caused seismic hazards. These earthquakes are called special earthquakes in this paper. For example, the Yishan earthquake of M.=2 and I=VI occurred on 25 Aug. 1980 and caused damage at a dam in the epicen-tral area, resulting in formation of a crack 27. 5 m in length and 5-7 cm in width on the dam and a fracture 10 -13 cm in width with horizontal dislocation of 15 cm and vertical dislocation of 2- 11 cm on the crest of the dam.
The special earthquakes are listed in the paper. The propagation velocity of seismic waves was analyzed in accordance with the properties of the karstic area . A maximum entropy spectral analysis of waveforms from the local earthquakes of same magnitude recorded in karstic and non -karstic areas indicates that : 1) The water-saturated karstic medium can amplify seismic waves; 2) The predominant period of seismic waves in karstic area is larger than that in non - karstic area . This predominant period reaches an intrinsic period of the buildings lower than three -storey ones. For this reason the seismic intensity tends to increase .
出处
《华南地震》
1992年第4期22-31,共10页
South China Journal of Seismology
关键词
地震
岩溶
地震波
震级
Special earthquakes , Guangxi, seismic wave amplification , karstic soft medium.
